Many mechanisms for indexing a table member are known. U.S. Pat. No. 3,381,578, granted to W. G. Buchanan, discloses an indexing means of the Geneva motion type. In the indexing means of the Geneva motion type, a driven wheel formed with radial slots is driven by a rotating cam having a drive pin. The drive pin is advanced to enter into one of the radial slots of the driven wheel so that the driven wheel is indexed by one pitch. However, with the indexing means of the Geneva motion type, a difficulty is encountered in that particular care must be paid in fabricating the above-mentioned Geneva motion elements, such as the rotating cam with a drive pin and a driven wheel, as well as in assembling the Geneva motion mechanism. This is because, otherwise, unfavorable impact motions between the driven wheel and the drive pin of the rotating cam will occur at the moment the indexing of the driven wheel is started or stopped. Further, when it is required to increase the number of radial slots of the driven wheel, the diameters of the driven wheel and the rotating cam must necessarily be increased. This fact results in an unfavorable increase in the size and shape of the indexing mechanism of the Geneva motion type. In addition, in the indexing means of the Geneva motion type, the rotating cam and the driven wheel are always arranged so that the axes of both rotating cam and driven wheel are transversely spaced apart from one another, resulting in an increase in the entire size and shape of the indexing mechanism.
On the other hand, U.S. Pat. No. 3,135,136, granted to M. B. MENTLEY, et al, discloses an indexing mechanism employing a fluid-operated cylinder as a power source for causing an indexing movement of the index member. In that indexing mechanism, the fluid operated cylinder provides movement for a feed pawl element, which in turn causes a rotational indexing motion of the index member. Therefore, a considerably complicated mechanism is indispensable in order that the rotational indexing motion of the index member be brought about by a linear motion of an output element of the fluid-operated cylinder. Further, in that indexing mechanism, prior to commencing of the indexing motion of the index member, a finger arm provided for maintaining the indexing position of the index member must be disengaged from the index member by employing a different fluid-operated cylinder. This fact not only adds to the complexity of the index mechanism, but also results in an increase in the manufacturing cost of the index mechanism.